2017 ASHS Annual Conference

Variability in autumn climate resulting in warmer and drier conditions can delay leaf senescence in deciduous fruit trees. As leaves remain for an extended season, trees may increase CO₂ assimilation and allow additional carbohydrate and nutrient mobilization to the reserves (stem and roots), which could later impact dormancy break and nutrient uptake in spring. In this study, we evaluated the physiological responses of two-year-old peach trees to fall temperatures and soil moisture on two peach cultivars (‘Scarletprince’ and ‘Autumnprince’ both on Guardian^TM rootstock). For each cultivar, we applied four treatments: 1) well-watered trees (100% ET_c needs) grown under ambient outdoor temperatures; 2) water deficient trees (50% ET_c needs), ambient outdoor temperatures; 3) well-watered trees grown in a greenhouse; and 4) water deficient trees in a greenhouse. Average temperature in the greenhouse was 5 °C warmer than ambient outdoor temperature. We measured gas exchange and nutrient concentration in leaves throughout autumn, and determined nutrient concentration in stem and root tissues during the winter to assess mobilization to the reserves. Although all trees within the greenhouse had delayed senescence, results show greenhouse-grown water deficient trees had significantly lower CO₂ assimilation (F = 4.8, P < 0.05) than trees under ambient outdoor conditions and well-watered trees in the greenhouse. Nevertheless, there were no significant differences in leaf number (F = 0.6, P > 0.05) or leaf area (F=2.3, P > 0.05). Provided differences between treatments regarding carbohydrates and remobilized nutrients, this study could provide a model for the larger climate change discussion within deciduous fruit tree cultivation and provide a platform for further research to optimize management practices encouraging environmental and orchard sustainability.